1. Field of the Invention
The present invention relates to a pallet assembly for substrate inspection device and a substrate inspection device.
2. Description of the Related Art
One of the display devices using a liquid crystal substrate is a flat panel display (hereinafter referred to as an FPD) This FPD is a display device for displaying electronic information. One of the recent typical FPDs is a liquid crystal display (hereinafter an LCD) composed of a thin film transistor (hereinafter a TFT). The LCD composed of the TFT is employed for a high performance laptop computer.
The constitution and the operation of the LCD composed of the TFT will be described below. The LCD composed of the TFT has a fundamental structure of a liquid crystal panel in which a liquid crystal is poured between one glass substrate on which the TFT and pixel electrodes are formed and the other glass substrate on which counter electrodes are formed. In this specification, the one glass substrate on which the TFT and pixel electrodes are formed is defined as a substrate.
FIG. 6 is a schematic view of a substrate on which the TFT and pixel electrodes are formed. In FIG. 6, the substrate 10 has a plurality of panels formed on a single glass substrate 11 through a process for manufacturing a typical integrated circuit, each panel 12 being composed of a plurality of pixels 13 arrayed like a matrix.
Each pixel 13 comprises a pixel electrode 14, a storage capacitor 15 and the TFT 16. The pixel electrode 14 is formed from a light transmitting material, typically, ITO (Indium Tin Oxide). An electrode having a reference voltage of the pixel 13 applied within the storage capacitor 15 is grounded. Namely, the reference voltage of each TFT 16 is set to a ground level. The TFT 16 functions as a switch. A row selection signal LR for switching control is supplied to a gate electrode G of the TFT 16, and a column selection signal LC as the data signal is supplied to a source electrode S of the TFT 16.
In driving the pixels 13, when a voltage VS is applied to the source electrode S of the TFT 16 (i.e., when the column selection signal LC is supplied), if a voltage VG is applied to the gate electrode G (i.e., when the row selection signal LR is supplied), the TFT 16 is turned on to increase the drain voltage VD. At this time, the storage capacitor 15 is charged to maintain a drain voltage VD till the next refresh cycle. By repeating this process for each pixel 13, a liquid crystal molecular array between two glass substrates is controlled to display a two-dimensional image on a liquid crystal display.
In the inspection of the substrate on which the TFT and pixel electrodes are formed, a method for determining a state of each pixel on the substrate without contact, employing the voltage contrast technique of electron beam was proposed U.S. Pat. No. 5,982,190). This substrate inspection method using the voltage contrast technique has the advantages that it is cheaper in the cost than the inspection method using the conventional mechanical probe, and faster in the inspection speed than the optical inspection method.
FIG. 7 is a view for explaining the substrate inspection method using the voltage contrast technique. This inspection method is made within a high vacuum chamber. The substrate to be inspected is conveyed to the high vacuum chamber, and inspected in a state where it is laid on the stage.
In FIG. 7, the inspection device comprises an electron beam generating source 21, a secondary electron detector 24 and a signal analyzer 25. The electron beam generating source 21 radiates an electron beam 22 to each pixel 13 of the substrate 10. The secondary electron detector 24 detects a secondary electron 23 generated by radiating the electron beam 22 to each pixel 13 of the substrate 10. Also, the secondary electron detector 24 outputs a signal representing a voltage waveform of pixel 13 to the signal analyzer 25 on the basis of the detected quantity of secondary electron 23. The signal analyzer 25 analyzes an output signal from the secondary electron detector 24 to inspect the state of pixel 13, particularly, the presence or absence or the content of defective pixel. Also, the signal analyzer 25 outputs a drive signal for electrically scanning each pixel 13 on the substrate 10 via a line 26. This scanning is performed in synchronism with the scanning on the substrate 10 as indicated by the arrow S with the electron beam 22.
A principle of the voltage contrast technique based on the detected quantity of secondary electron will be described below.
The quantity of secondary electron 23 discharged from each pixel 13 of the substrate 10 depends on an electrode for the voltage of pixel 13 on the substrate 10. For example, when the pixel 13 of the substrate 10 is driven positively, the secondary electron 23 generated by radiating the electron beam 22 to the pixel 13 has a negative electric charge, and is led into the pixel 13. As a result, the quantity of secondary electron 23 arriving at the secondary electron detector 24 is decreased.
On one hand, when the pixel 13 of the substrate 10 is driven negatively, the secondary electron 23 generated by radiating the electron beam 22 to the pixel 13 has a negative electric charge, and is repelled against the pixel 13. As a result, the quantity of secondary electron 23 generated from the pixel 13 arrives at the secondary electron detector 24.
In this manner, because the detected quantity of secondary electron 23 generated from the pixel 13 is affected by the polarity of voltage of the pixel 13, a voltage signal waveform of the pixel 13 is measured and the presence or absence of defective pixel is determined.
As above described, the inspection of the substrate is made within the high vacuum environment, and usually within a sealed chamber. Conventionally, this substrate was inspected in the state where it was laid directly on the stage within the chamber. In inspecting the substrate in this situation, the substrate might be broken within the sealed chamber, or a part of the apparatus comprising the chamber might be damaged. Namely, a glass substrate of the substrate might be fractured during the inspection, its fractions being scattered within the chamber to apart of the apparatus comprising the chamber, for example, a turbo molecular pump rotor for vacuum evacuation, damaging the apparatus. Also, it took a lot of trouble to draw back glass fractions scattered within the chamber and over the stage. Thus, it was apprehended conventionally that the apparatus might be damaged due to scattered fractions into the chamber or the withdrawal of fractions was made.
The present invention has been achieved in the light of the above affairs, and it is an object of the invention to provide a pallet assembly for substrate inspection device and a substrate inspection device for use with this pallet assembly, in which even when the substrate is broken with the inspection device, broken fractions can be easily withdrawn without damaging the inspection device.
In order to achieve the above object, this invention provides a substrate holding pallet assembly comprising a pallet for holding a substrate on upper face thereof, and a probe laid on said pallet from above so as to hold said substrate between said pallet and said probe.
It is preferable that concave grooves that receive conveyance unit for conveying the substrate are formed on the upper face of the pallet. In addition to this, one concave groove may be employed on the pallet.
Also, it is preferable that the pallet comprises a position alignment mechanism for aligning the position of the substrate on the pallet when the substrate is laid.
Also, it is preferable that the pallet comprises an electrode in contact with an external power supply, a feeding portion for applying a voltage from the electrode to a prober, and a flexible circuit for connecting the electrode with the feeding portion, and the prober comprises an electrode in contact with a feeding portion of the pallet, and probe pins for applying a voltage from the electrode to the substrate, the probe pins being mounted via an insulating member to the prober.
Also, in order to solve the above object, this invention provides a substrate inspection device comprising a chamber having an exhauster for exhausting the chamber into a high vacuum state, an electron beam generator for radiating an electron beam to the substrate, and a secondary electron detector for detecting a secondary electron generated from the substrate by radiation of electron beam from the electron beam generator, a pallet for holding the substrate on upper face thereof, and a probe laid on said pallet from above so as to hold said substrate between said pallet and said probe.
It is preferable that concave grooves that receive conveyance unit for conveying the substrate are formed on the upper face of the pallet.
Also, it is preferable that the pallet comprises a position alignment mechanism for aligning the position of the substrate on the pallet when the substrate is laid.
Also, it is preferable that the pallet comprises an electrode in contact with an external power supply, a feeding portion for applying a voltage from the electrode to a prober, and a flexible circuit for connecting the electrode with the feeding portion, and the prober comprises an electrode in contact with a feeding portion of the pallet, and probe pins for applying a voltage from the electrode to the substrate, the probe pins being mounted via an insulating member to the prober.
Also, it is preferable that the chamber is composed of a preliminary chamber having the exhauster and connected via an openable and closable first partition wall to the outside, and a main chamber having the electron beam generator and a secondary electron generator, and wherein the preliminary chamber and the main chamber are connected via an openable and closable second partition wall, and further comprising conveyance unit for conveying the pallet assembly between the preliminary chamber and the main chamber.
Also, it is preferable that at least two the preliminary chambers are provided for each one main chamber.
In the inspection device of the above constitution, even if the substrate is broken within the chamber, the fractions remain within the pallet assembly, and do not splash into the chamber. Accordingly, even if the glass substrate of the substrate is broken during the inspection, glass fractions do not splash into the chamber to damage a part of the device constituting the chamber.
Also, even if the glass substrate is broken within the chamber, the fractions do not splash into the chamber but remain within the pallet assembly, and thereby can be easily collected by withdrawing the pallet assembly.